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Color of Light Emitted by Led Depends on Mcq

The Light-Emitting Diode (LED) MCQ Quiz - Objective Question with Answer for The Light-Emitting Diode (LED) - Download Free PDF

Answer (Detailed Solution Below)

Option 1 : LED

The Light-Emitting Diode (LED) MCQ Question 1 Detailed Solution

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The correct answer is option 1, i.e. LED .

  • LED is the best source of light that consumes the least amount of energy.
    • LED is Light Emitting Diode whichemits light when current flows through it.
    • Itreleases energy in the form of photons.
  • The filament in an incandescent filament lamp is made of tungsten.

  • The compact fluorescent lamp is a low-pressure mercury-vapour gas-discharge lamp that uses fluorescence to produce visible light.

    • It producesshort-wave ultraviolet light.

Answer (Detailed Solution Below)

Option 1 : Forward biased

The Light-Emitting Diode (LED) MCQ Question 2 Detailed Solution

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CONCEPT :

EXPLANATION :

  • When an LED is reverse biased, then the free electrons (majority carriers) from n-side and holes (majority carriers) from the p-side will move away from the junction.
  • Due to this, the width of the depletion region increases, and no recombination of charge carriers occur and hence the LED will not emit light.
  • That's why LED can operate only in forward bias. So option 1 is correct.

EXTRA POINTS :

Theforward bias and reverse bias:

Answer (Detailed Solution Below)

Option 2 :

electrical energy into light energy

The Light-Emitting Diode (LED) MCQ Question 3 Detailed Solution

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The correct answer is electrical energy into light energy .

Key Points

  • LED (light-emitting diode)
    • The LED (light-emitting diode) is a PN junction device that emits light when a current passes through it in the forward direction, i.e. when LED is forward biased, it emits light.
    • In an LED, this energy lies in the visible region of electromagnetic radiation, and the photon released is perceived as light.
    • In reverse biased mode, it works like a normal diode and does not emit light.
    • It is an optical semiconductor device that emits light when voltage is applied means it converts electrical energy into light energy. Hence, Option 2 is correct.
    • When Light Emitting Diode (LED) is forward biased, the free electrons from the n-side and the holes from the p-side are pushed towards the junction.
    • Light-emitting diodes emit either visible light or invisible infrared light when forward biased.
    • The LEDs which emit invisible infrared light are used for remote controls.
    • LEDs that can emit red, yellow, orange, green, and blue light are available for commercial use.

The Light-Emitting Diode (LED) MCQ Question 4

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What is the difference between a CFL and an LED lamp?

1. To produce light, a CFL uses mercury vapour and phosphor while an LED lamp uses semiconductor material.

2. The average life span of a CFL is much longer than that of an LED lamp.

3. A CFL is less energy-efficient as compared to an LED lamp.

Which of the statements given above is/are correct?

  1. 1 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Answer (Detailed Solution Below)

Option 3 : 1 and 3 only

The Light-Emitting Diode (LED) MCQ Question 4 Detailed Solution

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The correct answer is 1 and 3 only .

Key Points

  • LED bulbs are much more efficient than CFL bulbs in terms of power consumption and life years. Hence Statement 3 is correct and 2 is Not Correct.

Important Points

LED

  • LED is known as "Light Emitting Diode".
  • A light-emitting diode (LED) is a two-lead semiconductor light source.
  • It is a p–n junction diode, which emits light when activated.
  • When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.
  • This effect is called electroluminescence, and the color of the light corresponds to the energy of the photon.

CFL

  • CFLs contain toxic mercury.
  • A fluorescent lamp is a low-pressure mercury-vapor gas-discharge lamp.
  • Electrons that are bound to mercury atoms are excited to states where they will radiate ultraviolet light as they return to a lower energy level.
  • This emitted ultraviolet light is converted into visible light as it strikes the fluorescent coating on the bulb (phosphor coating).

The Light-Emitting Diode (LED) MCQ Question 5:

Which of the following is the best source of light that consumes the least amount of energy?

  1. LED
  2. Filament lamp
  3. CFL
  4. Fluorescent lamp

Answer (Detailed Solution Below)

Option 1 : LED

The Light-Emitting Diode (LED) MCQ Question 5 Detailed Solution

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The correct answer is option 1, i.e. LED .

  • LED is the best source of light that consumes the least amount of energy.
    • LED is Light Emitting Diode whichemits light when current flows through it.
    • Itreleases energy in the form of photons.
  • The filament in an incandescent filament lamp is made of tungsten.

  • The compact fluorescent lamp is a low-pressure mercury-vapour gas-discharge lamp that uses fluorescence to produce visible light.

    • It producesshort-wave ultraviolet light.

The Light-Emitting Diode (LED) MCQ Question 6:

An LED is a photodiode which is _______________.

  1. lightly doped and under forward bias
  2. heavily doped and under forward bias
  3. heavily doped and under reverse bias
  4. lightly doped and under reverse bias

Answer (Detailed Solution Below)

Option 2 : heavily doped and under forward bias

The Light-Emitting Diode (LED) MCQ Question 6 Detailed Solution

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CONCEPT:

  • An LED is a heavily doped P-N junction diode which under forward biased condition emits spontaneous radiations and the wavelength of these radiations falls under wavelength in the visible spectrum.

EXPLANATION:

  • When the electric current passed through the LED then the electrons recombine with the holes present in the diode and hence LED emits the light.
  • The amount of light emitted will depend on the rate of doping, the diode allows the flow of current only when it is forward biased
  • Hence, the LED has to be forward biased and heavily doped
  • Hence, option 2 is the answer.

Additional Information

  • Longer life than other electrical light equipments
  • Emits monochromatic light
  • Environment friendly

The Light-Emitting Diode (LED) MCQ Question 7:

In a photodiode, light is focussed to fall on

  1. P-region only
  2. N-region only
  3. Full P and N regions
  4. Junction region only

Answer (Detailed Solution Below)

Option 4 : Junction region only

The Light-Emitting Diode (LED) MCQ Question 7 Detailed Solution

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CONCEPT :

  • Photodiode: A photodiode is a p-n junction fabricated from aphotosensitive semiconductor and provided with atransparent window to allow light tofall on itsjunction.
  • It is represented by

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EXPLANATION:

  • From the above diagram, it can be seen thatlight is focused to fall on its junction. So option 3 is correct.
  • A photodiode is generally operated in reverse bias condition.
  • The light when focused on the junction createselectron-hole pairs that result in the flow of electrons.

The Light-Emitting Diode (LED) MCQ Question 8:

LED is a p-n junction diode which is

  1. Forward biased
  2. Either forward biased or reverse biased
  3. Reverse biased
  4. Neither forward biased nor reverse biased

Answer (Detailed Solution Below)

Option 1 : Forward biased

The Light-Emitting Diode (LED) MCQ Question 8 Detailed Solution

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CONCEPT :

EXPLANATION :

  • When an LED is reverse biased, then the free electrons (majority carriers) from n-side and holes (majority carriers) from the p-side will move away from the junction.
  • Due to this, the width of the depletion region increases, and no recombination of charge carriers occur and hence the LED will not emit light.
  • That's why LED can operate only in forward bias. So option 1 is correct.

EXTRA POINTS :

Theforward bias and reverse bias:

The Light-Emitting Diode (LED) MCQ Question 9:

LED is a p-n junction diode which is

  1. Forward biased
  2. Reverse biased
  3. Both forward biased or reverse biased
  4. Neither forward biased nor reverse biased
  5. None of these

Answer (Detailed Solution Below)

Option 1 : Forward biased

The Light-Emitting Diode (LED) MCQ Question 9 Detailed Solution

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CONCEPT :

EXPLANATION :

  • When an LED is reverse biased, then the free electrons (majority carriers) from n-side and holes (majority carriers) from the p-side will move away from the junction.
  • Due to this, the width of the depletion region increases, and no recombination of charge carriers occur and hence the LED will not emit light.
  • That's why LED can operate only in forward bias. So option 1 is correct.

EXTRA POINTS :

Theforward bias and reverse bias:

The Light-Emitting Diode (LED) MCQ Question 10:

Light Emitting Diode (LED) converts ___________.

  1. light energy into electrical energy

  2. electrical energy into light energy

  3. thermal energy into light energy
  4. mechanical energy into electrical energy

Answer (Detailed Solution Below)

Option 2 :

electrical energy into light energy

The Light-Emitting Diode (LED) MCQ Question 10 Detailed Solution

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The correct answer is electrical energy into light energy .

Key Points

  • LED (light-emitting diode)
    • The LED (light-emitting diode) is a PN junction device that emits light when a current passes through it in the forward direction, i.e. when LED is forward biased, it emits light.
    • In an LED, this energy lies in the visible region of electromagnetic radiation, and the photon released is perceived as light.
    • In reverse biased mode, it works like a normal diode and does not emit light.
    • It is an optical semiconductor device that emits light when voltage is applied means it converts electrical energy into light energy. Hence, Option 2 is correct.
    • When Light Emitting Diode (LED) is forward biased, the free electrons from the n-side and the holes from the p-side are pushed towards the junction.
    • Light-emitting diodes emit either visible light or invisible infrared light when forward biased.
    • The LEDs which emit invisible infrared light are used for remote controls.
    • LEDs that can emit red, yellow, orange, green, and blue light are available for commercial use.

Color of Light Emitted by Led Depends on Mcq

Source: https://testbook.com/objective-questions/mcq-on-the-light-emitting-diode-led--5eea6a1339140f30f369efb2